Yet Another Crank But No-Start Thread

Robio5150

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@Igoo65, @Jerry Bransford, whomever else...- I would PM you about this thread but I don't see that feature on this forum. YES, I've read through numerous posts here and on other forums. My situation seems to be bit different, I've tried to provide exhaustive data up front so someone can "walk into the movie halfway" and lend me their expertise. i'm a pretty competent moderately skilled shade tree mech. and have had 2 buddies with more knowledge than me get stumped over this one. Pardon the description but it addreses questions that might initially be asked. THANKS IN ADVANCE for y'alls help.

I have a painfully similar Crank-No-Start situation with my '05 LJ 4.0 6 spd.
  • Jeep ran perfectly well when parked last Oct.
  • Parked, battery disconnected, no trickle charger (until 6th month till just before trans reinstall)
  • Removed trans for reverse gear fix,
  • I DID perform some wiring harness cleanup/repair while trans was out. Split the tape and plastic loom cover in many places and re-loomed with new plastic and high-temp tape. I was extremely careful when spliting loom. I doubt I even nicked a wire but.....anything is possible. Maybe I wrapped new tape and loom too tight? I'm pretty meticulous about such things.
  • After re-install of transmission, dismal "crank-no-start" condition.
  • I have performed the litany of diags and thrown CKPS (x3-original, Napa,Chrysler/Mopar), CPS, and now PCM. No change.
  • The VERY odd thing to all of this...It has actually started 3 times and idled for 15-20 mins ea. time and ran like a sewing machine. Then upon shut down...crank-no-start again.
  • Codes initially thrown were CKPS/CPS but those have been cleared and have NOT come back, subsequent code re: PCM not talking to SKIM module, Check Gauges,
  • To best of my ability metered and verified 5v at CKPS harness at sensor location and verified 5v at CPS harness connection.
  • All relays swapped with working "horn" relay
  • SPARK test on coil rail resulted in NO verified spark on all locations but one, via plug grounded to block and in-line spark node light. One anomaly, most forward plug location had weak, intermittent spark (both test methods)??
  • I've laid under Jeep and wiggled CKPS harness while someone cranked-to see if wiring had shorts or breaks. No change-I DID perform some wiring harness cleanup/repair while trans was out. Split the tape and plastic loom cover in many places and re-loomed with new plastic and high-temp tape. I was extremely careful when spliting loom. I doubt I even nicked a wire but.....
  • Buddy w/$3K scanner go no CKPS/CPS codes when he did diag.
  • Some gauge failure and SKIM key light intermittently appear. But not consistently.
  • One theory-PCM back up batteries dead too long it no longer able to communicate with SKIM and other components-plausible? Even "New" re-flashed PCM exhibits same results.
  • Second theory- possible CKPS harness short or break-but again, doesn't seem likely- no melting or visible chafing.
LASTLY -remember the Jeep, after dozens (+-) of cranks in a row has started and run strong, for 15-20 at a time. 3X's !!!
Help plz!
 

Chris

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Just to rule out the obvious, I assume you did your homework and replaced all sensors with OE Mopar replacement sensors, correct?
 

Jamison C

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Here’s my personal takeaway from this.

If the SKIM light is intermittently showing, it sounds like there’s an issue there. I’ve never heard of the computer or module going bad regarding SKIM, so it’s possible your key was going bad which is why it started sometimes and then didn’t. If you try to start the Jeep enough times without the coded key, your PCM will lock the engine out of starting and you have to take it to a dealer to have everything reset.

It doesn’t matter how long you let it sit or if you ground out the PCM. Unless one of your buddies has a DRB scanner I don't think there’s any way to DIY reset the SKIM.
 
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Robio5150

Robio5150

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Just to rule out the obvious, I assume you did your homework and replaced all sensors with OE Mopar replacement sensors, correct?
yup, kinda buried in my post : thrown in CKPS (x3-original, Napa,Chrysler/Mopar),
 
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Robio5150

Robio5150

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Here’s my personal takeaway from this.

If the SKIM light is intermittently showing, it sounds like there’s an issue there. I’ve never heard of the computer or module going bad regarding SKIM, so it’s possible your key was going bad which is why it started sometimes and then didn’t. If you try to start the Jeep enough times without the coded key, your PCM will lock the engine out of starting and you have to take it to a dealer to have everything reset.

It doesn’t matter how long you let it sit or if you ground out the PCM. Unless one of your buddies has a DRB scanner I don't think there’s any way to DIY reset the SKIM.

Hey @Jamison C and @Daryl the same buddy that did some diag with $3K scanner was actually a locksmith as well. He tried several differnt combos of newly SKIMMED keys, original keys, all while alternating orig. PCM and then reman (flashed) PCM. So yeah, he did alot. He said it just appeared that the PCM wasn't talking to the SKIM and that had to be reset by Jeep dealer :( Again, funny enough, after 12+ cranks it started to cough, then out of nowhere it started right up. He said "I really don't know if I did anything or not" It idled for 20 mins just fine, then idle all of the sudden shot up to 2k and STAYED there no matter what. So I hopped in to drive it home (finally, from my buddy's shop) and it felt like it was in "limp" mode. No real acceleration, struggled to reach 35-40 and topped out. But everytime I put clutch in, it would rev to 2K all the way home. It hasn't started since (3 attempts)
Thanks for trying to help me out y'all !!!!
I really don't want to take this Jeep to the dealer that's close-they ...are....awful. I used to be a service advisor, they are terrible.
 

JMT

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I'm sure you checked, but you've got good fuel pressure at the rail?
 
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Robio5150

Robio5150

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I'm sure you checked, but you've got good fuel pressure at the rail?
Hey JMT thaks for asking.
I've done no "official" FP check at fuel rail, my rail is the oh- so- convenient fuel rail with NO shrader valve/port. Not even sure how I'd do that. That being said, I get:
A. Audible FP prime when turning key to "ON"
B. Lots of Fuel smell (till noxious) after several crank attempts
C. Have sprayed starter fluid directly into TB and doesn't induce ANY change. No farting, burping or coughing from engine.
D. Have verified to the best of my diag abilities (listed in OP) I find NO spark at Ignition coil rail BUT this Jeep has started 3 times and idled just fine.
 
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Robio5150

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Wish I could look at it in person. Can you post some pictures of your engine compartment from different angles? Any pictures of the wiring you repaired?
Hey Da-rill :) I might have some shots of after I re-wrapped the harness while trans was out. I'll try to get some posted. I appreciate your willingness to help, wish soemone could take a first hand look too. I've got some pretty savvy tech buddies and we're ALL scratching our heads. This Jeep ran fine when I parked it to do trtans work, the ony thing I messed with that would have to do with ginition/starting is the removal of CKPS and re-wrap of CKPS harness. I'm stumped.
 

Daryl

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Hey Da-rill :) I might have some shots of after I re-wrapped the harness while trans was out. I'll try to get some posted. I appreciate your willingness to help, wish soemone could take a first hand look too. I've got some pretty savvy tech buddies and we're ALL scratching our heads. This Jeep ran fine when I parked it to do trtans work, the ony thing I messed with that would have to do with ginition/starting is the removal of CKPS and re-wrap of CKPS harness. I'm stumped.
Since it ran fine until you worked on it, it’s most likely something you unintentionally did with the wiring.
 

JMT

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Hey JMT thaks for asking.
I've done no "official" FP check at fuel rail, my rail is the oh- so- convenient fuel rail with NO shrader valve/port. Not even sure how I'd do that. That being said, I get:
A. Audible FP prime when turning key to "ON"
B. Lots of Fuel smell (till noxious) after several crank attempts
C. Have sprayed starter fluid directly into TB and doesn't induce ANY change. No farting, burping or coughing from engine.
D. Have verified to the best of my diag abilities (listed in OP) I find NO spark at Ignition coil rail BUT this Jeep has started 3 times and idled just fine.
If you’re not getting spark at ignition coil rail, BUT you are sometimes. What? Battery cables?
 
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Robio5150

Robio5150

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Since it ran fine until you worked on it, it’s most likely something you unintentionally did with the wiring.
Hey Daryl, It's looking like I may have to get under it again and see if I can peel back the new tape and loom covering I put on. I was super careful while splitting and reparing the harness but, who knows, could have had a sketchy wire already and I moved it just enough to create a tiny break. I've actually layed under the Jeep while buddy cranked it and wriggled the harness all around the area, no change. I appreciate you volunteering to come to TN and help, that's mighty nice of you:) Wish me luck this weekend!
 
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Robio5150

Robio5150

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If you’re not getting spark at ignition coil rail, BUT you are sometimes. What? Battery cables?
Hey JTM, I inspected, cleaned and lubed the battery cables/terminals before the very first start, after Jeep sat w/battery disconnected. I've metered voltage all over and get 14.5 most places on + and have done continuity checks on all visible grounds - When I do crank it, I get super strong starter crank for 8-9 cranks, then of course the cranking starts to slow a bit a battery drains. All behaves and sounds normal though. Thanks for your help.